Obesity is a serious public health threat in the US with 31% of the population affected. Links between obesity and depression have been observed in clinical and epidemiological studies, particularly among women. For example, between 25-50% of treatment-seeking obese women were found to have a history of major depressive disorder (MOD). Obesity and depression have been studied independently, so very little is known about the optimal treatment approach for this comorbidity that largely affects women. The literature and our preliminary data reveal shared symptomatology across obesity and depression. Both conditions appear to be characterized by inactivity, anhedonia (loss of interest or pleasure in daily activities), reduced exercise self-efficacy, and mood-regulatory eating. These shared symptoms along with depressed mood are predictors of worse outcomes in standard weight loss treatments among women. In a preliminary study of a standard weight loss treatment, obese patients with comorbid MOD only achieved about half the weight loss of their nondepressed counterparts. Facilitating weight loss for patients with comorbid MOD and obesity may require a tailored treatment that targets the shared symptomatology. Behavioral activation (BA) for depression may be a potentially useful adjunct to weight loss treatment when obesity is comorbid with MOD because it specifically targets anhedonia, activity levels, and mood regulation, issues common to both conditions. In a feasibility study we developed a 12-week behavioral activation-modified weight loss intervention that targets diet, lifestyle activity, and mood regulation. Results support the feasibility of this approach and potential efficacy on both weight and depression outcomes. However, we observed that weight loss accelerated after depressive symptoms improved. Both our quantitative and qualitative data suggest that a staggered approach where depressive counseling precedes weight loss counseling may the optimal sequencing for treatment. In a randomized clinical trial (RCT), the present study aims to test whether among depressed obese women, adding behavioral activation to weight control treatment facilitates greater weight loss than weight control treatment alone. Women (n=174) from the University of Massachusetts Memorial Health Care system who meet criteria for both MOD and obesity will be randomized to one of two weight loss interventions: 1) BA-modified weight treatment condition (BA) or 2) standard weight treatment condition (ST). Outcomes will be assessed at 6-months, 1- and 2-years after randomization. Secondary outcomes include depression, physical activity, caloric intake, psychosocial variables (anhedonia, exercise self-efficacy, disinhibited eating, quality of life), and cardiovascular risk factors (blood pressure, serum lipids, C-reactive protein).